ULDs are standard sized containers and pallets commonly used to load luggage or other cargo onto aircraft. ULDs allow quantities of cargo to be bundled into a single unit, simplifying the aircraft loading and unloading process. Ground transportation of ULDs at airports typically occurs by loading ULDs on dollies, and towing the dollies using tugs. Ground transportation of ULDs outside of airports typically occurs by loading ULDs on flatbed trailers towed by conventional motorized truck-tractor units. A typical flatbed trailer is either 48 feet or 53 feet in length, 8 feet and 6 inches in width, and the current lowest legal height limit in any US state without needing a permit is 13 feet 6 inches. Using IATA ULD codes, examples of ULDs follow. Containers which are 125 inches in length and 88 inches wide are the AAD and AAX which are both 96 inches high, the AAZ which is 64 inches high, and the AAY which is 81 inches high. Containers which are 125 inches in length and 96 inches wide are the AMJ and AMA which are both 96 inches high, and the AMX which is 118 inches high. The ALP container is 125 inches long, 61 inches high, and 64 inches high. The AKE container (also known in the industry as a LD3) is 62 inches long, 61 inches wide, and 64 inches high. It is noted that 2 AKE containers can be palletized and netted or strapped thereon, for example on a single PAG or PAH flat pallet with a length of 125 inches and a width of 88 inches, and take up the same space on the trailer as one AAD container. Another flat pallet option is the PMC pallet with a length of 125 inches and a width of 96 inches.
It was realized by the inventors of the present disclosure that improvements in ground transportation for ULDs are needed to increase efficiency and provide other important advantages.